Selective Surface Modification of Biopolymers

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Selective Surface Modification of Biopolymers

• REU Progress Presentation
• Presented by Alicia Certain
• Advisor Jeffrey Youngblood
• August 4, 2004

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Polymers vs. Biopolymers

• Familiar examples garbage bags, milk jugs, car
  bumpers, motor oil, carpet fibers, plumbing pipes
• Biopolymers The green materials
• Made from renewable resources
• Biodegradable
• Have different properties than traditional
  polymers

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Wettability and Applications

• An increase in wettability would be desirable for
  applications such as textiles, cleaning wipes,
  household fabrics
• A decrease in wettability would be desired for
  packaging

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The First Biopolymer

• Family of polyhydroxyalkanoates (PHAs)
• Worked with poly(lactic acid) (PLA)
• Trade name Natureworks
• Produced from corn

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The Next Polymer

• From the family of 1,3, propanediol
• Specific polymer is poly(propylene-terephthalate)
  (PPT)
• Trade name Sorona
• Also comes from corn

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Modification of Biopolymers

• Samples were spin coated onto glass slides
• Goal was to modify the surface of the polymers in
  order to change wettability
• Worked with three chemical modifications
• APTES
• Hydrolysis
• Aminolysis

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APTES modification

• 3-aminopropyltriethoxysilane
• Previously used to modify PET
• Increased wettability
• What will it do to biopolymers?

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Hydrolysis

• Immersion in aqueous alkaline base
• Breaks up chain, adding hydroxyl group to one
  end, hydrogen to the other
• Should increase wettability
• Simplest procedure

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Aminolysis

• Similar to hydrolysis, using an amine instead
• Tried n-butylamine, which is known to increase
  wettability in PET very slow!
• Used n-lithiodiamine to decrease reaction times

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Contact Angle Analysis

• Liquid drop on solid surface modifies its shape
  based on the interfacial tensions
• Creates a material property of the system called
  the contact angle

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Characterization

• Contact angle measurements primary
  characterization
• Tests done through the goniometer
• AFM imaging used to augment

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Wettability Results
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Untreated PLA
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2 minutes
15
15 minutes
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Optimal Times
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Wettability Results
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Contact Angles
30 minutes
15 minutes
45 minutes
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Wettability Results
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Wettability Results
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PPT and APTES

• Most successful in decreasing wettability
• 6 hours led to approx. 55 degree advancing, 0
  receding
• 24 hours led to approx. 45 degree advancing, 0
  receding
• 72 hours created an increase back to approx. 60
  advancing, 0 receding

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Flourinated APTES

• 24 hour APTES reaction on PLA with concentration
  cut in half
• Subsequent reaction with tridecaflouro-1,1,2,2-tet
  rahydrooctyltri-chlorosilane
• APTES on PLA only increases wettability slightly,
  but surface is functionalized and flourination
  successfully decreases wettability

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Possible Future Directions

• APTES optimization
• Pinpointing a more definite optimum PLA
  hydrolysis time
• Vapor phase reactions
• Subsequent reactions on functionalized surfaces
  to increase hydrophobicity rather than decrease

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Thanks!

• Prof. Youngblood and Prof. Kvam
• John, Ben, and Phil
• Allen and Kendra
• The REU Group